The current beta version of MathJax 2.6 implements a new renderer that is faster and can be rendered on the server side:
Improved CommonHTML output. The CommonHTML output now provides the same layout quality and MathML support as the HTML-CSS and SVG output. It is on average 40% faster than the other outputs and the markup it produces are identical on all browsers and thus can also be pre-generated on the server via MathJax-node.
Using server-side rendering of MathJax it wouldn't be necessary to load the js library and do all the processing on the client just to view MathJax, it would only be necessary if you actually edit or interact with the formulas. Visitors that simply view a few pages would never even need to load the MathJax library.
This would also allow for question titles with MathJax to be displayed correctly on sites that don't have MathJax enabled, which is a problem with the hot questions list.
Server-side rendering would also provide the option to allow sites the use of MathJax where it was previously too expensive compared to the small amount of posts that actually needed it.
I know that this is likely a pretty large project, but as SE tends to value site performance highly I think it might be worth it. There are currently 29 sites that use MathJax on the network, so this would affect a large part of the entire network.